| 1. |
- Bagheri, Niusha, et al.
(author)
-
Change in the emission saturation and kinetics of upconversion nanoparticles under different light irradiations
- 2019
-
In: Optical materials (Amsterdam). - : Elsevier. - 0925-3467 .- 1873-1252. ; 97
-
Journal article (peer-reviewed)abstract
- Nd3+-sensitized upconversion nanoparticles (UCNPs) can be excited by both 980 and 808 nm light, which is regarded as a particularly advantageous property of these particles. In this work, we demonstrate that the nanoparticles can exhibit significantly different response when excited at these two excitation wavelengths, showing dependence on the intensity of the excitation light and the way it is distributed in time. Specifically, with 808 nm excitation saturation in the emitted luminescence is more readily reached with increasing excitation intensities than upon 980 nm excitation. This is accompanied by delayed upconversion luminescence (UCL) kinetics and weaker UCL intensities. The different luminescence response at 808 and 980 nm excitation reported in this work is relevant in a manifold of applications using UCNPs as labels and sensors. This could also open new possibilities for multi-wavelength excitable UCNPs for upconversion color display and in laser-scanning microscopy providing selective readouts and sub-sectioning of samples.
|
|
| 2. |
- Bergstrand, Jan, et al.
(author)
-
On the decay time of upconversion luminescence
- 2019
-
In: Nanoscale. - : Royal Society of Chemistry. - 2040-3364 .- 2040-3372. ; 11:11, s. 4959-4969
-
Journal article (peer-reviewed)abstract
- In this study, we systematically investigate the decay characteristics of upconversion luminescence (UCL) under anti-Stokes excitation through numerical simulations based on rate-equation models. We find that a UCL decay profile generally involves contributions from the sensitizer's excited-state lifetime, energy transfer and cross-relaxation processes. It should thus be regarded as the overall temporal response of the whole upconversion system to the excitation function rather than the intrinsic lifetime of the luminescence emitting state. Only under certain conditions, such as when the effective lifetime of the sensitizer's excited state is significantly shorter than that of the UCL emitting state and of the absence of cross-relaxation processes involving the emitting energy level, the UCL decay time approaches the intrinsic lifetime of the emitting state. Subsequently, Stokes excitation is generally preferred in order to accurately quantify the intrinsic lifetime of the emitting state. However, possible cross-relaxation between doped ions at high doping levels can complicate the decay characteristics of the luminescence and even make the Stokes-excitation approach fail. A strong cross-relaxation process can also account for the power dependence of the decay characteristics of UCL.
|
|
| 3. |
- Huang, Fuhua, et al.
(author)
-
Morphology controlled synthesis of Fe3+-doped upconversion nanomaterials
- 2024
-
In: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 14:8, s. 4990-5000
-
Journal article (peer-reviewed)abstract
- This work details the synthesis of paramagnetic upconversion nanoparticles doped with Fe3+ in various morphologies via the thermal decomposition method, followed by comprehensive characterization of their structures, optical properties and magnetism using diverse analytical techniques. Our findings demonstrate that by precisely modulating the ratio of oleic acid to octadecene in the solvent, one can successfully obtain hexagonal nanodiscs with a consistent and well-defined morphology. Further adjustments in the oleic acid to octadecene ratio, coupled with fine-tuning of the Na+/F− ratio, led to the production of small-sized nanorods with uniform morphology. Significantly, all Fe3+-doped nanoparticles displayed pronounced paramagnetism, with magnetic susceptibility measurements at 1 T and room temperature of 0.15 emu g−1 and 0.14 emu g−1 for the nanodiscs and nanorods, respectively. To further enhance their magnetic properties, we replaced the Y-matrix with a Gd-matrix, and by fine-tuning the oleic acid/octadecene and Na+/F− ratios, we achieved nanoparticles with uniform morphology. The magnetic susceptibility was 0.82 emu g−1 at 1 T and room temperature. Simultaneously, we could control the nanoparticle size by altering the synthesis temperature. These upconversion nanostructures, characterized by both paramagnetic properties and regular morphology, represent promising dual-mode nanoprobe candidates for optical biological imaging and magnetic resonance imaging.
|
|
| 4. |
- Ji, Yanan, et al.
(author)
-
Cascade photon upconversion amplification for selective multispectral narrow-band near-infrared photodetection
-
Other publication (other academic/artistic)abstract
- Facing the fact that selective detection of multiple narrow spectral bands in the near-infrared (NIR) region still poses a fundamental challenge, we have, in this work, developed NIR photodetectors (PDs) using photon upconversion nanocrystals (UCNCs) combined with perovskite films. In order to conquer the relatively high pumping threshold of UCNCs, we designed a novel cascade amplification strategy for upconversion luminescence (UCL) through cascading the superlensing effect of dielectric microlens arrays and the plasmonic effect of gold nanorods, which readily leads to a UCL enhancement by more than four orders of magnitude under weak light irradiation. By accommodating multiple optical active lanthanide ions in a core-shell-shell hierarchical architecture, the developed PDs on top can detect three well-separated narrow bands in the NIR region, i.e., 808, 980, and 1540 nm, respectively. Due to the large UCL enhancement, the obtained PDs demonstrate extremely high responsivity of 30.73, 23.15, 12.20 A/W and detectivity of 5.36, 3.45, 1.91x10^11 Jones for the 808, 980, and 1540 nm light detection, respectively, together with short response times in the range of 80-120 ms. Moreover, we demonstrate for the first time that the response to the excitation modulation frequency of a PD can be employed to discriminate the incident light wavelength. We believe that our work provides a novel insight for developing NIR PDs, and that it can spur the development of other applications using upconversion nanotechnology.
|
|
| 5. |
- Ji, Yanan, et al.
(author)
-
Huge upconversion luminescence enhancement by a cascade optical field modulation strategy facilitating selective multispectral narrow-band near-infrared photodetection
- 2020
-
In: Light. - : SPRINGERNATURE. - 2095-5545 .- 2047-7538. ; 9:1
-
Journal article (peer-reviewed)abstract
- Since selective detection of multiple narrow spectral bands in the near-infrared (NIR) region still poses a fundamental challenge, we have, in this work, developed NIR photodetectors (PDs) using photon upconversion nanocrystals (UCNCs) combined with perovskite films. To conquer the relatively high pumping threshold of UCNCs, we designed a novel cascade optical field modulation strategy to boost upconversion luminescence (UCL) by cascading the superlensing effect of dielectric microlens arrays and the plasmonic effect of gold nanorods, which readily leads to a UCL enhancement by more than four orders of magnitude under weak light irradiation. By accommodating multiple optically active lanthanide ions in a core-shell-shell hierarchical architecture, developed PDs on top of this structure can detect three well-separated narrow bands in the NIR region, i.e., those centered at 808, 980, and 1540 nm. Due to the large UCL enhancement, the obtained PDs demonstrate extremely high responsivities of 30.73, 23.15, and 12.20 A W-1 and detectivities of 5.36, 3.45, and 1.91 x 10(11) Jones for 808, 980, and 1540 nm light detection, respectively, together with short response times in the range of 80-120 ms. Moreover, we demonstrate for the first time that the response to the excitation modulation frequency of a PD can be employed to discriminate the incident light wavelength. We believe that our work provides novel insight for developing NIR PDs and that it can spur the development of other applications using upconversion nanotechnology. Cascade amplified upconversion luminescence: Applied in narrow band NIR photodetection Selective detection of multiple narrow spectral bands in the near-infrared (NIR) region is still a challenge. Recently, Hongwei Song and Wen Xu at Jilin University/China, Haichun Liu at KTH Royal Institute of Technology/Sweden, and their co-workers have successfully fabricated a novel multiple NIR bands photo-detectors (PDs) by combining multiple-excitation-bands core-shell upconversion nanocrystals (UCNCs) with MAPbI(3) perovskite photoelectric conversion layer. Through a cascade optical field modulation strategy, a combination of microlenses and gold plasmon nanocrystals, the emission intensity of the UCNCs and the photoelectric signal of the PDs can be enhanced four orders of magnitude. Moreover, the excitation frequency of the PD has been employed to discriminate the wavelength of incident light for the first time. This work provides a novel insight for developing multiple bands NIR PDs, and for applications of upconversion nanotechnology.
|
|
| 6. |
- Ji, Yanan, et al.
(author)
-
Perovskite photonic crystal photoelectric devices
- 2022
-
In: Applied Physics Reviews. - : AIP Publishing. - 1931-9401. ; 9:4
-
Research review (peer-reviewed)abstract
- Metal halide perovskite materials have been extensively explored in modern photonic devices. Photonic crystals (PCs) are periodic structures with specific optical properties, such as photonic stop bands and "slow photon " effects, which can tailor the propagation and distribution of photons in photoelectric devices. PCs have in recent years been widely explored to significantly improve the performance of perovskite luminescent materials and/or photoelectric devices. Therefore, a full understanding of the key role of PCs and a further learning of the correct use of PCs in perovskite photonic/photoelectric devices are essential for realizing the inherent potential of the superior performance of such devices. By means of this first review, we aim at offering a comprehensive framework description for PCs suitable for high-performance perovskite photoelectric devices. We start with a brief introduction to the basic aspects of PCs. Then, we summarize the influences of PCs on emission/absorption for perovskite luminescent materials. Subsequently, we systematically discuss concepts like light extraction, light trapping, slow-light effects, and structural effects of PCs for perovskite devices, with a particular emphasis on their theoretical descriptions. We argue that the marriage of perovskite materials with PCs can open up a novel frontier in photoelectric devices that potentially can spawn many exciting new fields.
|
|
| 7. |
- Labrador-Páez, Lucia, et al.
(author)
-
Excitation Pulse Duration Response of Upconversion Nanoparticles and Its Applications
- 2022
-
In: Journal of Physical Chemistry Letters. - : American Chemical Society (ACS). - 1948-7185 .- 1948-7185. ; 13:48, s. 11208-11215
-
Journal article (peer-reviewed)abstract
- Lanthanide-doped upconversion nanoparticles (UCNPs) have rich photophysics exhibiting complex luminescence kinetics. In this work, we thoroughly investigated the luminescence response of UCNPs to excitation pulse durations. Analyzing this response opens new opportunities in optical encoding/decoding and the assignment of transitions to emission peaks and provides advantages in applications of UCNPs, e.g., for better optical sectioning and improved luminescence nanothermometry. Our work shows that monitoring the UCNP luminescence response to excitation pulse durations (while keeping the duty cycle constant) by recording the average luminescence intensity using a low-time resolution detector such as a spectrometer offers a powerful approach for significantly extending the utility of UCNPs.
|
|
| 8. |
- Liu, Qingyun, 1993-, et al.
(author)
-
High throughput decoding approach for luminescencekinetics-based optical encoding of lanthanide upconversion nanoparticles
-
Other publication (other academic/artistic)abstract
- Lanthanide upconversion nanoparticles (UCNPs) are increasingly explored to develop high-security-level anti-counterfeiting and multiplexing applications, due to the availability of ample encoding dimensions. Among other applications, upconversion luminescence(UCL) kinetics-based optical encoding is particularly attractive as it provides an almost unlimited encoding capacity due to the ease of manipulating the UCL kinetics by chemical engineering. However, current decoding methods limit its applications because of a typically low throughput and high cost of the system. In this Letter, we propose a novel decoding approach for UCL kinetics-based optical encoding, which utilizes a pulsed excitation source with adjustable pulse duration and a low time-resolution and large-area detector. We develop a theoretical fitting model and show how fingerprint time constants of the UCNPs (the encoding identities) can be extracted from the correlation between the averaged UCL intensity and the pulse duration. Our new approach provides a high-throughput and cost-effective solution to decode UCL kinetics.
|
|
| 9. |
- Liu, Qingyun, et al.
(author)
-
Microlens array enhanced upconversion luminescence at low excitation irradiance
- 2019
-
In: Nanoscale. - : ROYAL SOC CHEMISTRY. - 2040-3364 .- 2040-3372. ; 11:29, s. 14070-14078
-
Journal article (peer-reviewed)abstract
- The dearth of high upconversion luminescence (UCL) intensity at low excitation irradiance hinders the prevalent application of lanthanide-doped upconversion nanoparticles (UCNPs) in many fields ranging from optical bioimaging to photovoltaics. In this work, we propose to use microlens arrays (MLAs) as spatial light modulators to manipulate the distribution of excitation light fields in order to increase UCL, taking advantage of its nonlinear response to the excitation irradiance. We show that multicolored UCL from NaYF4:Yb3+,Er3+@NaYF4:Yb3+,Nd3+ and NaYF4:Yb3+,Tm3+@NaYF4:Yb3+,Nd3+ core/shell UCNPs can be increased by more than one order of magnitude under either 980 or 808 nm excitation, by simply placing a polymeric MLA onto the top of these samples. The observed typical green (525/540 nm) and red (654 nm) UCL bands from Er3+ and a blue (450/475 nm) UCL band from Tm3+ exhibit distinct enhancement factors due to their different multi-photon processes. Importantly, our ray tracing simulation reveals that the MLA is able to spatially confine the excitation light (980 and 808 nm) by orders of magnitude, thus amplifying UCL by more than 225-fold (the 450 nm UCL band of Tm3+) at low excitation irradiance. The proposed MLA method has immediate ramifications for the improved performance of all types of UCNP-based devices, such as UCNP-enhanced dye sensitized solar cells demonstrated here.
|
|
| 10. |
- Liu, Qingyun
(author)
-
Studies of optical properties of lanthanide upconversion nanoparticles for emerging applications.
- 2020
-
Doctoral thesis (other academic/artistic)abstract
- YTTERBY, a small village very close to Stockholm where I live, is the place in the world which has lent its name to the largest number of elements in the periodic table, namely four - YTTRIUM, YTTERBIUM, ERBIUM and TERBIUM. Three more lanthanide elements were discovered from the now empty quarry located in this village. By the time of their discoveries in the 19th century little could be known about their fantastic properties, the versatility of their use and functionality in what we now call nanotechnology. This is a circumstance that motivated me to rather recently enter lanthanide research, in particular studies of their outstanding optical properties for the purpose of information technology and energy harvesting.So far, upconversion nanoparticles (UCNPs) have been much explored as unique spectral converters for various applications, like biotechnology, information technology and photovoltaic devices due to properties like sharp emission profiles, low autofluorescence and large anti-Stoke shifts. Still, there is much to explore and to understand in order to fully utilize the very unique properties of UCNPs. The kinetic dynamics of the upconversion process is one such aspect that is not well understood, and a deeper understanding of the kinetic dynamics of lanthanide upconversion systems could thus broaden their applications. Therefore, the work of this thesis is focused on investigating the kinetic dynamics of upconversion processes mainly based on systems with NaYF4 as host material, and Yb3+/Er3+ or Yb3+/Tm3+ embedded as sensitizer/activator. Through rate equation models, the kinetic dynamics of upconversion are comparatively investigated with numerical simulations and analytical derivation. The temporal response regarding upconverted luminescence and quantum yield power density dependence, excitation duration response and excitation frequency response of the upconversion systems are investigated and the corresponding applications for multicolor imaging, optical encoding, photovoltaics, IR photodetectors are explored and analyzed in the thesis, taking advantage of the kinetic properties.
|
|
